Security grille and manufacturing method

Abstract

A security grille is disclosed in which corresponding ends of rods, preferably of square cross-sectional shape, are clamped by initially-separate halves of clamps. The halves of each clamp become connected permanently to one another by a nub/bolt combination, wherein the nut has a drive head which shears off when the connection has been properly made. In one embodiment, the clamp halves are made by drop-stamping and the rods are made from hot-rolled steel bars. Alternatively, the clamp halves may be made as pressings and the rods may be made from cold-drawn steel bars. The clamp halves are provided with decorative covers.

I claim: 
     
       1. A security grille adapted for fixing to a structure so as to extend across an aperture therein, said grille including at least one pair of rods whose corresponding one ends are adapted to be fixed to said structure and whose corresponding other ends are adapted to be connected to one another by two initially separate portions of a device which are subsequently so permanently joined to one another as to clamp said other ends between them, each of said two separate portions including a central portion and a plurality of channel-shaped limbs extending radially outwardly from said central portion, each limb having a proximal end attached to said central portion and a free distal end, said other ends of said pair of rods being placed between an associated pair of inwardly facing channel-shaped limbs comprising one limb from each of said two separate portions, the respective free distal ends of said associated pair of limbs being canted toward one another with respect to said respective central portions, whereby the respective free distal ends exert a clamping force on the rod ends when the two separate portions of the device are joined together. 
     
     
       2. A grille as claimed in claim 1, and comprising two pairs of rods with one pair arranged on a first straight line which is normal to a second straight line on which the other pair is arranged, the corresponding one ends of the four rods being fixed to said structure and the corresponding other ends of the four rods being connected to one another by the portions of said device. 
     
     
       3. A grille as claimed in claim 2, wherein said initially separate portions of each device are identical with one another, each portion being bored and counterbored centrally and also being provided with recesses which are formed in one face of the portion and which radiate from the centre of the portion and which are for the accommodation of said other ends. 
     
     
       4. A grille as claimed in claim 1, and comprising a plurality of rods and a plurality of devices, each of which devices comprises two initially separate portions which have been permanently joined to one another, all of said rods having a first end thereof clamped between the two portions of a respective one of said devices, some of said rods having the second end thereof clamped between the two portions of a respective other of said devices, and some of said rods having the second end thereof fixed to said structure. 
     
     
       5. A grille as claimed in claim 4, wherein the rods are of square cross-sectional shape. 
     
     
       6. A grille as claimed in claim 1, wherein each of said devices has its two initially separate portions permanently joined to one another by means of a nut and bolt, the head of the bolt having its axially outer surface flush with that of one of the portions, and the axially outer surface of the nut being flush with that of the other of the portions as a result of an hexagonal drive head of said nut having sheared off when the critical torsional load has been applied to said drive head. 
     
     
       7. A grille as claimed in claim 1, wherein said device has a cruciform shape. 
     
     
       8. A security grille which comprises an assembly of one or more clamps and a number of bars, at least some of the ends of said bars being clamped by the clamp(s) and some of the bars having ends which are adapted to facilitate the fixing of the security grille to a building; each clamp comprising two half-clamps and each half-clamp having a number of channel-shaped limbs; said limbs being connected to one another to form a central portion of the half-clamp; the central poriton being apertured in order to accept a fixing screw or bolt; that part of each channel which forms the bottom thereof lying, in said central portion of the half-clamp, on a plane; the free end portions of the channel-shaped limbs being canted away from said plane in the direction in which the walls of the respective channel are directed; whereby two such half-clamps, so placed on the ends of bars that said ends are enclosed by the channels formed by the facing channel-shaped limbs and securely connected to one another by nut-and-bolt means, exert a clamping action on said bar ends as a result of the canted free end portions of the channel-shaped limbs of each half-clamp being forced against the bar end in such a way as to be flexed towards the plane of the central portion of the respective half-clamp. 
     
     
       9. A security grille as claimed in claim 8, wherein each free end portion of each channel-shaped limb is canted at an angle of about 4°-5° away from the plane on which the central portion of the half-clamp lies. 
     
     
       10. A security grille as claimed in claim 8, wherein the bars are made of cold-drawn steel and the half-clamps are made as pressings. 
     
     
       11. A security grille as claimed in claim 8, wherein said nut and bolt means comprises a bolt having its axially outer surface flush with that of one of the portions, and the axially outer surface of the nut being flush with that of the other of the portions as a result of a hexagonal drive head of said nut having sheared off when the critical torsional load has been applied to said drive head. 
     
     
       12. A security grille as claimed in claim 8, wherein said half-clamps have a cruciform shape.